Electrophotography-based additive manufacturing with part molding

ABSTRACT

An additive manufacturing method produces a 3D part utilizes electrophotography-based additive manufacturing and molding processes. A layered structure having a cavity is printed on a build platform using at least one electrophotographic (EP) engine to develop imaged layers of powder material, and a transfusion assembly to stack and fuse the imaged layers on the build platform. Molding material is deposited into the cavity as the layered structure is printed, using a deposition unit. The molding material solidifies to form at least a portion of the 3D part, which may also include portions formed from imaged powder material.

BACKGROUND

The present disclosure relates to systems and methods for manufacturing3D parts through a combination of electrophotography-based additivemanufacturing processes and molding processes.

Additive manufacturing is generally a process in which athree-dimensional (3D) object is manufactured utilizing a computer modelof the objects. A basic operation of an additive manufacturing systemconsists of slicing a three-dimensional computer model into thin crosssections, translating the result into two-dimensional position data, andfeeding the data to control equipment which manufacture athree-dimensional structure in a layerwise manner using one or moreadditive manufacturing techniques. Additive manufacturing entails manydifferent approaches to the method of fabrication, including fuseddeposition modeling, ink jetting, selective laser sintering,powder/binder jetting, electron-beam melting, electrophotographicimaging, and stereolithographic processes.

In an electrophotographic 3D printing or production process, each sliceof the digital representation of the 3D part is printed or developedfrom powder materials using an electrophotographic engine. Theelectrophotographic engine generally operates in accordance with 2Delectrophotographic printing processes, using charged powder materialsthat are formulated for use in building a 3D part (e.g., a polymerictoner material). The electrophotographic engine typically uses aconductive support drum that is coated with a photoconductive materiallayer, where latent electrostatic images are formed by electrostaticcharging, followed by image-wise exposure of the photoconductive layerby an optical source. The latent electrostatic images are then moved toa developing station where the charged powder is applied to chargedareas, or alternatively to discharged areas of the photoconductiveinsulator to form the layer of the charged powder material representinga slice of the 3D part. The developed layer is transferred to a transfermedium, from which the layer is transfused to previously printed layerswith heat and/or pressure to build the 3D part.

In fabricating 3D parts by depositing layers of a part material,supporting layers or structures are typically built underneathoverhanging portions or in cavities of objects under construction, whichare not supported by the part material itself. The support structure istypically built utilizing the same deposition techniques by which thepart material is deposited. The support material adheres to the partmaterial during fabrication, and is removable from the completed 3D partwhen the printing process is complete.

SUMMARY

Aspects of the present disclosure are directed to systems and methodsfor manufacturing 3D parts through a combination ofelectrophotography-based additive manufacturing processes and moldingprocesses. In some embodiments of the method of producing a 3D partusing electrophotography-based additive manufacturing and moldingprocesses, a mold structure is built or printed having a cavity on abuild platform using at least one electrophotographic (EP) engine and atransfusion assembly. Molding material is then deposited into the cavityusing a deposition unit to form the 3D part.

One embodiment of an additive manufacturing system for producing 3Dparts includes an electrophotographic engine and a deposition unit. Theelectrophotography unit includes a transfer assembly including atransfer medium, at least one EP engine configured to develop layers ofa powder material, and a transfusion assembly configured to build a moldstructure having a cavity on a build platform in a layer-by-layer mannerby transfusing the developed layers to each other. The deposition unitis configured to deposit molding material into the cavity and form amolded part portion of the 3D part within the cavity.

Definitions

Unless otherwise specified, the following terms as used herein have themeanings provided below:

The term “copolymer” refers to a polymer having two or more monomerspecies, and includes terpolymers (i.e., copolymers having three monomerspecies).

The terms “at least one” and “one or more of” an element are usedinterchangeably, and have the same meaning that includes a singleelement and a plurality of the elements, and may also be represented bythe suffix “(s)” at the end of the element. For example, “at least onepolyimide”, “one or more polyamides”, and “polyamide(s)” may be usedinterchangeably and have the same meaning.

The terms “preferred” and “preferably” refer to embodiments of theinvention that may afford certain benefits, under certain circumstances.However, other embodiments may also be preferred, under the same orother circumstances. Furthermore, the recitation of one or morepreferred embodiments does not imply that other embodiments are notuseful, and is not intended to exclude other embodiments from the scopeof the present disclosure.

Directional orientations such as “above”, “below”, “top”, “bottom”, andthe like are made with reference to a direction along a printing axis ofa 3D part. In the embodiments in which the printing axis is a verticalz-axis, the layer-printing direction is the upward direction along thevertical z-axis. In these embodiments, the terms “above”, “below”,“top”, “bottom”, and the like are based on the vertical z-axis. However,in embodiments in which the layers of 3D parts are printed along adifferent axis, the terms “above”, “below”, “top”, “bottom”, and thelike are relative to the given axis.

The term “providing”, such as for “providing a material” and the like,when recited in the claims, is not intended to require any particulardelivery or receipt of the provided item. Rather, the term “providing”is merely used to recite items that will be referred to in subsequentelements of the claim(s), for purposes of clarity and ease ofreadability.

Unless otherwise specified, temperatures referred to herein are based onatmospheric pressure (i.e. one atmosphere).

The terms “about” and “substantially” are used herein with respect tomeasurable values and ranges due to expected variations known to thoseskilled in the art (e.g., limitations and variabilities inmeasurements).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram of an exemplary additive manufacturingsystem for producing 3D parts and associated support structures, inaccordance with embodiments of the present disclosure.

FIG. 2 is a schematic view of an exemplary electrophotographic engine ofthe system for developing layers of the support material.

FIG. 3 is a schematic front view of an exemplary electrophotographyengine, which includes an intermediary drum or belt.

FIG. 4 is a schematic front view of an exemplary transfusion assembly ofthe system for performing layer transfusion steps with the developedlayers.

FIG. 5 is a simplified diagram of a deposition unit and exemplary methodsteps of a part molding process in accordance with embodiments of thepresent disclosure.

FIGS. 6-11, which are simplified side cross-sectional views of acombined structure 16 at various stages of production.

FIG. 12 is a simplified top view of an exemplary structure supported ona build platform after completing multiple transfusion processes and oneor more molding processes, in accordance with embodiments of the presentdisclosure.

FIG. 13 is a simplified cross-sectional view of the exemplary structuretaken generally along lines 13-13 of FIG. 12.

DETAILED DESCRIPTION

As mentioned above, during a electrophotographic 3D part additivemanufacturing or printing operation, an electrophotographic (EP) enginemay develop each layer of the 3D part (part portions) and associatedsupport structures (support structure portions) out of powder materials(e.g., polymeric toners) using the electrophotographic process. Thedeveloped layers are then transferred to a transfer medium, whichdelivers the layers to a transfusion assembly where the layers aretransfused together (e.g., using heat and/or pressure) to build the 3Dpart and support structures in a layer-by-layer manner. The supportstructures are later removed (e.g., dissolved) to reveal the completed3D part.

Electrophotography is sensitive to numerous characteristics of thepowder material used to form the part and support portions. Theseinclude the charge-to-mass ratio (Q/M), size, surface, morphology,roundness, flow, and infrared absorption. Additionally, the supportstructure material must be compatible with the part material (including,for example, the pressures and temperatures at which the part materialfuses), while also being removable after the part is built (for example,soluble in a solution that will not affect the part material). Thematerials for use in electrophotographic part building processes must beprecisely matched for use with the hardware components of theelectrophotography-based additive manufacturing system. As a result ofthe numerous variables, the selection of materials available for forming3D parts using the electrophotographic process are limited, oradditional cost is necessary in their creation.

Embodiments of the present disclosure are a hybrid system that utilizesthe electrophotographic manufacturing process to print or build a moldstructure in a layer-by-layer manner in coordination with using anon-electrophotographic process to produce a 3D part, or a moldedportion of a 3D part, within the mold structure. This allows formanufacturing of parts out of materials that are not compatible with theelectrophotographic manufacturing process used to build the supportstructure. Additionally, this gives flexibility to sharp melting pointmaterials (crystalline materials) that may have less latitude inpressure settings relative to the support material.

FIG. 1 is a simplified diagram of an exemplary additive manufacturingsystem 10 for producing 3D parts and associated support structures usingelectrophotographic and molding processes. System 10 includes anelectrophotography-based additive manufacturing unit (EP unit) 12 and adeposition unit 14. The EP unit 12 provides imaged powder layers oftoner material that undergo a transfusion process in order to build EPlayers of a combined structure 16 having a cavity 18 that defines a partmold. The deposition unit 14 forms a molded part portion of thestructure 16 by depositing molding material 20 into the cavity 18.

As discussed in greater detail below, these EP structure building andmolding processes may be performed on a layer-by-layer basis to form thefinal 3D part. That is, the EP unit 12 may form at least one layer,generally referred to as EP layer 22, of the structure 16 that defines aportion of the desired cavity or part mold 18. The deposition unit 14 isthen used to apply the molding material 20 into the cavity 18 to formthe molded part portion. Additional EP layers 22 may then be formed overthe previously built EP layers 22 and the molded part portions thatdefine another portion of the desired cavity or part mold 18 using theEP unit 12. The deposition unit 14 may then deposit molding material 20into the new cavity 18 to form another layer of the molded part. Thedeposited layers of molding material 20 may be courser than the EPlayers 22, and they may be deposited only after several EP layers 22 aretransfused to form a mold cavity. These steps may be repeated asnecessary until the structure 16 is completely formed. Afterward,portions of the electrophotographically built structure 16 may beremoved by, for example, dissolving or disintegrating sacrificialmaterial portions of the structure 16 in an aqueous solution ordispersion, to complete the production of a final produced 3D part thatincludes the molded part. In some embodiments, the EP layers 22 of theEP printed structure 16 may include printed part portions along withsacrificial portions, wherein the printed part portions are combinedwith the molded part portions to form the final produced 3D part.

In some embodiments, the system 10 includes a controller 26, whichrepresents one or more processors that are configured to executeinstructions, which may be stored locally in memory of the system 10 orin memory that is remote to the system 10, to control components of thesystem 10 to perform one or more functions described herein. In someembodiments, the controller 26 includes one or more control circuits,microprocessor-based engine control systems, and/or digitally-controlledraster imaging processor systems, and is configured to operate thecomponents of system 10 in a synchronized manner based on printinginstructions received from a host computer 28 or a remote location. Insome embodiments, the host computer 28 includes one or morecomputer-based systems that are configured to communicate withcontroller 26 to provide 3D part printing instructions (and otheroperating information). For example, the host computer 28 may transferinformation to the controller 26 that relates to the sliced layers ofthe 3D parts and support structures, thereby allowing the system 10 toproduce the 3D parts and support structures in a layer-by-layer manner.

Exemplary embodiments of the EP unit 12 will initially be described withreference to FIGS. 1-4. In some embodiments, the EP unit 12 includes oneor more EP engines, generally referred to as 32, a transfer assembly 34,biasing mechanisms 36, and a transfusion assembly 40, as shown inFIG. 1. Examples of suitable components and functional operations forthe EP unit 12 include those disclosed in Hanson et al., U.S. Pat. Nos.8,879,957 and 8,488,994.

The EP engines 32 image or otherwise develop the layers 22 of powdermaterials, where the powder materials are each preferably engineered foruse with the particular architecture of each of the EP engines 32. Asdiscussed below, the developed EP layers 22 may be transferred to atransfer medium 44 of the transfer assembly 34, which delivers thelayers 22 to the transfusion assembly 40. The transfusion assembly 40operates to build or print the 3D structure 16, which may includesupport structures, part structures that form a portion of the 3D partbeing produced, and/or other structures, in a layer-by-layer manner bytransfusing the layers 22 together on a build platform 48.

In some embodiments, the transfer medium 44 includes a belt, as shown inFIG. 1. Examples of suitable transfer belts for the transfer medium 44include those disclosed in Comb et al. U.S. Publication Nos.2013/0186549 and 2013/0186558. In some embodiments, the belt 44 includesfront surface 44 a and rear surface 44 b, where front surface 44 a facesthe EP engines 12, and the rear surface 44 b is in contact with thebiasing mechanisms 36.

In some embodiments, the transfer assembly 34 includes one or more drivemechanisms that include, for example, a motor 50 and a drive roller 52,or other suitable drive mechanism, and operate to drive the transfermedium or belt 44 in a feed direction 53. In some embodiments, thetransfer assembly 34 includes idler rollers 54 that provide support forthe belt 44. The exemplary transfer assembly 34 illustrated in FIG. 1 ishighly simplified and may take on other configurations. Additionally,the transfer assembly 34 may include additional components that are notshown in order to simplify the illustration, such as, for example,components for maintaining a desired tension in the belt 44, a beltcleaner for removing debris from the surface 44 a that receives thelayers 22, and other components.

The EP unit 12 includes at least one EP engine 32 s that develops layersof powder support material. In some embodiments, the one or more EPengines 32 shown in FIG. 1 may include one or more EP engines 32 thatdevelop layers of powder part material, and are generally referred toherein as EP engines 32 p. In some embodiments, the EP engine 32 s ispositioned upstream from a corresponding EP engine 32 p relative to thefeed direction 53, as shown in FIG. 1. In alternative embodiments, thearrangement of the EP engines 32 p and 32 s may be reversed such thatthe EP engine 32 p is upstream from the EP engine 32 s relative to thefeed direction 53. In further alternative embodiments, EP unit 12 mayinclude three or more EP engines 32 for printing layers of additionalmaterials, as indicated in FIG. 1, or it may include only EP engine 32s.

FIG. 2 is a schematic front view of the EP engines 32 s and 32 p of theEP unit 12, in accordance with exemplary embodiments of the presentdisclosure. In the shown embodiment, the EP engines 32 p and 32 s mayinclude the same components, such as a photoconductor drum 62 having aconductive body 64 and a photoconductive surface 66. The conductive body64 is an electrically-conductive body (e.g., fabricated from copper,aluminum, tin, or the like), that is electrically grounded andconfigured to rotate around a shaft 68. The shaft 68 is correspondinglyconnected to a drive motor 70, which is configured to rotate the shaft68 (and the photoconductor drum 62) in the direction of arrow 72 at aconstant rate. While embodiments of the EP engines 32 are discussed andillustrated as utilizing a photoconductor drum 62, a belt having aconductive material, or other suitable bodies, may also be utilized inplace of the photoconductor drum 62 and the conductive body 64.

The photoconductive surface 66 is a thin film extending around thecircumferential surface of the conductive body 64, and is preferablyderived from one or more photoconductive materials, such as amorphoussilicon, selenium, zinc oxide, organic materials, and the like. Asdiscussed below, the surface 66 is configured to receive latent-chargedimages of the sliced layers of a 3D part or support structure (ornegative images), and to attract charged particles of the part orsupport material to the charged or discharged image areas, therebycreating the layers of the 3D part or support structure.

As further shown, each of the exemplary EP engines 32 p and 32 s alsoincludes a charge inducer 74, an imager 76, a development station 78, acleaning station 80, and a discharge device 82, each of which may be insignal communication with the controller 26. The charge inducer 74, theimager 76, the development station 78, the cleaning station 80, and thedischarge device 82 accordingly define an image-forming assembly for thesurface 66 while the drive motor 70 and the shaft 68 rotate thephotoconductor drum 62 in the direction 72.

The EP engines 32 use the charged particle or powder material(s) (e.g.,polymeric or thermoplastic toner), generally referred to herein as 86,to develop or form the EP layers 22. For example, the image-formingassembly for the surface 66 of the EP engine 32 s is used to formsupport layers 22 s of the powder support material 86 s, where a supplyof the support material 86 s may be retained by the development station78 (of the EP engine 32 s) along with carrier particles. Similarly, theimage-forming assembly for the surface 66 of the EP engine 32 p is usedto form part layers 22 p of the powder part material 86 p, where asupply of the part material 86 p may be retained by the developmentstation 78 (of the EP engine 32 p) along with carrier particles.

The charge inducer 74 is configured to generate a uniform electrostaticcharge on the surface 66 as the surface 66 rotates in the direction 72past the charge inducer 74. Suitable devices for the charge inducer 74include corotrons, scorotrons, charging rollers, and other electrostaticcharging devices.

The imager 76 is a digitally-controlled, pixel-wise light exposureapparatus configured to selectively emit electromagnetic radiationtoward the uniform electrostatic charge on the surface 66 as the surface66 rotates in the direction 72 the past imager 76. The selectiveexposure of the electromagnetic radiation to the surface 66 is directedby the controller 26, and causes discrete pixel-wise locations of theelectrostatic charge to be removed (i.e., discharged, thereby forminglatent image charge patterns on the surface 66.

Suitable devices for the imager 76 include scanning laser (e.g., gas orsolid state lasers) light sources, light emitting diode (LED) arrayexposure devices, and other exposure device conventionally used in 2Delectrophotography systems. In alternative embodiments, suitable devicesfor the charge inducer 74 and the imager 76 include ion-depositionsystems configured to selectively directly deposit charged ions orelectrons to the surface 66 to form the latent image charge pattern. Assuch, as used herein, the term “electrophotography” can broadly beconsidered as “electrostatography,” or a process that produces a chargepattern on a surface. Alternatives also include such things asionography.

Each development station 78 is an electrostatic and magnetic developmentstation or cartridge that retains the supply of the powdered partmaterial 86 p or the support material 86 s, along with carrierparticles. The development stations 78 may function in a similar mannerto single or dual component development systems and toner cartridgesused in 2D electrophotography systems. For example, each developmentstation 78 may include an enclosure for retaining the part material 86 por the support material 86 s and carrier particles. When agitated, thecarrier particles generate triboelectric charges to attract the powdersof the part material 86 p or the support material 86 s, which chargesthe attracted powders to a desired sign and magnitude, as discussedbelow.

Each development station 78 may also include one or more devices fortransferring the charged material to the surface 66, such as conveyors,fur brushes, paddle wheels, rollers, and/or magnetic brushes. Forinstance, as the surface 66 (containing the latent charged image)rotates from the imager 76 to the development station 78 in thedirection 72, the support material 86 s is attracted to theappropriately charged regions of the latent image on the surface 66,utilizing either charged area development or discharged area development(depending on the electrophotography mode being utilized). This createssuccessive layers 22 s as the photoconductor drum 62 continues to rotatein the direction 72, where the successive layers 22 s correspond to thesuccessive sliced layers of the digital representation of the 3D part orsupport structure.

The successive layers 22 p or 22 s are then rotated with the surface 66in the direction 72 to a transfer region in which layers 22 p or 22 sare successively transferred from the photoconductor drum 62 to the belt44 or other transfer medium. While illustrated as an engagement betweenthe photoconductor drum 62 and the belt 44, in some preferredembodiments, the EP engines 32 p and 32 s may also include intermediarytransfer drums and/or belts, as discussed further below. In otherembodiments, the photoconductive drum 62 may engage directly with atransfer drum of the transfusion assembly 40 (thus obviating the needfor transfer assembly 34).

After a given layer 22 p or 22 s is transferred from the photoconductordrum 62 to the belt 44 (or an intermediary transfer drum or belt), as adrive motor 70 rotates the shaft 68 and the photoconductor drum 62 inthe direction 72 such that the region of the surface 66 that previouslyheld the layer 22 p or 22 s passes the cleaning station 80. The cleaningstation 80 is a station configured to remove any residual,non-transferred portions of part or support material 86 p or 86 s.Suitable devices for the cleaning station 80 include blade cleaners,brush cleaners, electrostatic cleaners, vacuum-based cleaners, andcombinations thereof.

After passing the cleaning station 80, the surface 66 continues torotate in the direction 72 such that the cleaned regions of the surface66 pass the discharge device 82 to remove any residual electrostaticcharge on the surface 66, prior to starting the next cycle. Suitabledevices for the discharge device 82 include optical systems,high-voltage alternating-current corotrons and/or scorotrons, one ormore rotating dielectric rollers having conductive cores with appliedhigh-voltage alternating-current, and combinations thereof.

The biasing mechanisms 36 are configured to induce electrical potentialsthrough the belt 44 to electrostatically attract the layers 22 p and 22s from the EP engines 32 p and 32 s to the belt 44. Because the layers22 p and 22 s are each only a single layer increment in thickness atthis point in the process, electrostatic attraction is suitable fortransferring the layers 22 p and 22 s from the EP engines 32 p and 32 sto the belt 44.

The controller 26 preferably rotates the photoconductor drums 62 of theEP engines 32 p and 32 s at the same rotational rates that aresynchronized with the line speed of the belt 44 and/or with anyintermediary or alternative transfer drums or belts. This allows the EPunit 12 to develop and transfer the layers 22 p and 22 s in coordinationwith each other from separate developer images. In particular, as shown,each part layer 22 p may be transferred to the belt 44 with properregistration with each support layer 22 s to produce a combined part andsupport material layer, which is generally designated as EP layer 22.

As can be appreciated, some of the EP layers 22 transferred to the layertransfusion assembly 40 may only include support material 86 s or mayonly include part material 86 p, depending on the particular geometriesof the structure 16 and layer slicing. This may eliminate the necessityof registering layers 22 s or 22 p printed using different engines 32.Furthermore, when the system 100 only includes or uses one EP engines 32s to print single-material EP layers 22, registering different portionsof each layer 22 may be avoided.

In a further alternative embodiment, one or both of the EP engines 32 pand 32 s may also include one or more intermediary transfer drums and/orbelts between the photoconductor drum 62 and the belt or transfer medium44. For example, as shown in FIG. 3, the EP engine 32 s may also includean intermediary drum 62 a that rotates in the direction 72 a thatopposes the direction 72, in which drum 62 is rotated, under therotational power of motor 70 a. The intermediary drum 62 a engages withthe photoconductor drum 62 to receive the developed layers 22 s from thephotoconductor drum 62, and then carries the received developed layers22 s and transfers them to the belt 44. When present in the system 100,an EP engine 32 p may include the same arrangement of an intermediarydrum 62 a for carrying the developed layers 22 p from the photoconductordrum 62 to the belt 44. The use of such intermediary transfer drums orbelts for the EP engines 32 p and 32 s can be beneficial for thermallyisolating the photoconductor drum 62 from the belt 44, for example.

FIG. 4 illustrates an exemplary embodiment for the layer transfusionassembly 40. As shown, the transfusion assembly 40 includes the buildplatform 48, a nip roller 90, a layer heater 92, top-of-part heater 94,and an optional post-transfusion heater 96. The build platform 48 is aplatform assembly or platen of the EP unit 12 that is configured toreceive the heated EP layers 22 for printing or building the structure16, which may include part portions 22 p of the 3D part, and/or supportportions 22 s, in a layer-by-layer manner. In some embodiments, thebuild platform 48 may include removable film substrates (not shown) forreceiving the printed layers 22, where the removable film substrates maybe restrained against build platform using any suitable technique (e.g.,vacuum).

The structure 16 illustrated in FIG. 4 includes EP layers 22 havingportions 22 sp, that represent either support portions 22 s or partportions 22 p. Thus, the structure 16 illustrated in FIG. 4 represents astructure 16 that is formed entirely of support portions 22 s, and astructure 16 that includes both support portions 22 s and part portions22 p. Portions 22 sp are also shown in other figures to illustrate thesealternative options for the structure 16 and the individual layers 22forming the structure 16.

The build platform 48 is supported by a gantry 104 or other suitablemechanism, which is configured to move the build platform 48 along abuild path 106 that traverses the z-axis and the x-axis, as illustratedschematically in FIGS. 1 and 4. In some embodiments, the gantry 104 maymove the platform 48 along the build path 106 in a reciprocatingrectangular pattern where the primary motion is back-and-forth along thex-axis, as illustrated in FIG. 4. The gantry 104 may be operated by amotor 108 based on commands from the controller 26, where the motor 108may be an electrical motor, a hydraulic system, a pneumatic system, orthe like.

In some embodiments, the build platform 48 includes a heating element110 (e.g., an electric heater), as illustrated in FIG. 4. The heatingelement 110 may be configured to heat and maintain the build platform 48at an elevated temperature that is greater than room temperature (25°C.), such as at a desired average temperature of the structure 16, asdiscussed in Comb et al. U.S. Publication No. 2013/0186549.

The nip roller 90 is an exemplary pressing element or elements, which isconfigured to rotate around a fixed axis with the movement of the belt44. In particular, the nip roller 90 may roll against the rear surface44 b in the direction of arrow 112 while the belt 44 rotates in the feeddirection 53. In some embodiments, the nip roller 90 includes a heatingelement 114 (e.g., an electric heater). The heating element 114 isconfigured to heat and maintain nip roller 90 at an elevated temperaturethat is greater than room temperature (25° C.), such as at a desiredtransfer temperature for the EP layers 22.

The layer heater 92 includes one or more heating devices (e.g., aninfrared heater and/or a heated air jet) that are configured to heat theEP layers 22 on the belt 44 to a temperature at or above an intendedtransfer temperature of the EP layer 22, such as a fusion temperature ofthe part material 86 p and/or the support material 86 s, prior toreaching the nip roller 90. Each EP layer 22 desirably passes by (orthrough) the layer heater 92 for a sufficient residence time to heat thelayer 22 to the intended transfer temperature. The top-of-part heater 94may function in a similar manner as the layer heater 92, and heats thetop surfaces of the structure 16 on the build platform 48 to an elevatedtemperature, such as at or above a fusion temperature (or other suitableelevated temperature) of the powder material.

If a part material is printed using a EP engine, the support material 86s of the present disclosure used to form the support layers or portions22 s preferably has a melt rheology that is similar to or substantiallythe same as the melt rheology of the part material 86 p of the presentdisclosure used to form the part layers or portions 22 p of thestructure 16. This allows the part and support materials 86 p and 86 sof the layers 22 p and 22 s to be heated together to substantially thesame transfer temperature, and also allows the part and supportmaterials 86 p and 86 s at the top surfaces of the structure 16 to beheated together by top-of-part heater 94 to substantially the sametemperature. Thus, the part layers 22 p and the support layers 22 s maybe transfused together to the top surfaces of the structure 16 supportedon the platform 48 in a single transfusion step as the combined EP layer22 using the transfusion assembly 40. However, the part material 86 p isoptional and, therefore, support materials 86 s of any suitable rheologyis within the scope of the present disclosure. For example, multiple EPengines 32 s that produce layers 22 s formed of a single supportmaterial 86 s may also be used.

The optional post-transfusion heater 96 may be located downstream fromnip roller 90 relative to the feed direction 53, and is configured toheat the transfused layers 22 to an elevated temperature. Again, closemelt rheologies of the part and support materials 86 p and 86 s willallow the post-transfusion heater 96 to post-heat the top surfaces ofthe structure 16, such as part portions 22 p and support structureportions 22 s, together in a single post-fuse step when part material 86p is utilized.

As mentioned above, in some embodiments, prior to building the combinedstructure 16 on the build platform 48, the build platform 48 and the niproller 90 may be heated to desired temperatures. For example, the buildplatform 48 may be heated to the average part temperature of structure16. In comparison, the nip roller 90 may be heated to a desired transfertemperature for the EP layers 22. During the printing or transferringoperation, the belt 44 carries an EP layer 22 past the layer heater 92,which may heat the layer 22 and the associated region of the belt 44 toat or above the transfer temperature. Suitable transfer temperatures forthe charged powder materials of the present disclosure includetemperatures that exceed the glass transition temperature of thesematerials, where the layer 22 is softened but not melted.

As further shown in FIG. 4, during operation, the gantry 104 may movethe build platform 48 with the current structure 16 in a reciprocatingrectangular build pattern 86. In particular, the gantry 104 may move thebuild platform 48 along the x-axis below, along, or through thetop-of-part heater 94. The heater 94 heats the intermediate top surfacesof the current structure 16 to an elevated temperature, such as at orabove the transfer temperatures of the part and support materials 86 pand 86 s. The heaters 92 and 94 may heat the EP layers 22 and the topsurfaces of the current structure 16 to about the same temperatures toprovide a consistent transfusion interface temperature. Alternatively,the heaters 92 and 94 may heat layers 22 and the top surfaces of thepart portions 22 p and the support portions 22 s to differenttemperatures to attain a desired transfusion interface temperature.

The continued rotation of the belt 44 and the movement of the buildplatform 48 align the heated EP layer 22 with the heated top surfaces ofthe structure 16 with proper registration along the x-axis. The gantry104 may continue to move the build platform 48 along the x-axis, at arate that is synchronized with the rotational rate of the belt 44 in thefeed direction 53 (i.e., the same directions and speed). This causes therear surface 44 b of the belt 44 to rotate around the nip roller 90 tonip the belt 44 and the heated layer 22 against the top surfaces ofstructure 16. This presses the heated layer 22 between the heated topsurfaces of the structure 16 at the location of the nip roller 90, whichat least partially transfuses the heated layer 22 to the top layers ofthe structure 16.

As the transfused layer 22 passes the nip of the nip roller 90, the belt44 wraps around the nip roller 90 to separate and disengage from thebuild platform 48. This assists in releasing the transfused layer 22from the belt 44, allowing the transfused layer 22 to remain adhered tothe structure 16. Maintaining the transfusion interface temperature at atransfer temperature that is higher than its glass transitiontemperature, but lower than its fusion temperature, allows the heatedlayer 22 to be hot enough to adhere to the structure 16, while alsobeing cool enough to readily release from the belt 44. In alternativeembodiments, nip roller 90 may be replace with multiple nip rollers(e.g., a pair of nip rollers), or by a press plate, such as aredisclosed in Chillscyzn et al. U.S. Pat. No. 8,718,522. In otheralternative embodiments, as mentioned above, the transfer assembly 34may be eliminated, and the belt 44 and nip roller 90 replaced with atransfer drum or other transfer medium configured to receive imagedlayers from the EP engines 32, such as is disclosed in Hanson et al.,U.S. Pat. No. 8,879,957. In such embodiments, the imaged layers may beheated while on the transfer drum.

After release from the belt 44 or other transfer medium, in someembodiments, the gantry 104 continues to move the build platform 48along the x-axis to the post-transfusion heater 96. At post-transfusionheater 96, the top-most layers 22 of the structure 16 may be heated toat least the fusion temperature of the thermoplastic-based powder in apost-fuse or heat-setting step. This melts the material of thetransfused EP layer 22 to a highly fusable state such that polymermolecules of the transfused layer 22 quickly interdiffuse to achieve ahigh level of interfacial entanglement with the support structure 16.

In some embodiments, the transfusion assembly 40 includes a coolingdevice, shown as chiller 116, configured to cool the top layers 22 ofthe structure 16 on the platform 48, such as using air jets, as thegantry 104 moves the build platform 48 along the build path 106. Toassist in keeping the structure 16 at the average part temperature, insome preferred embodiments, the heater 94 and/or the heater 96 may beconfigured to heat only the top-most layers of structure 16. Forexample, in embodiments in which heaters 92, 94, and 96 are configuredto emit infrared radiation, the part and support materials 86 p and 86 smay include heat absorbers and/or other colorants configured to restrictpenetration of the infrared wavelengths to within only the top-mostlayers. Alternatively, the heaters 92, 94, and/or 96 may be configuredto blow heated air across the top surfaces of the structure 16. Ineither case, limiting the thermal penetration into the structure 16allows the top-most layers to be sufficiently transfused, while alsoreducing the amount of cooling required to keep the structure 16 at thedesired average part temperature.

After the transfusion of the EP layer 22 to the structure 16 supportedon the build platform 48, the gantry 104 may move the build platform andthe supported structure 16 to the deposition unit 14. The depositionunit 14 then performs a molding process to form a molded part portion 22mp within the one or more cavities 18 of the layer 22, as illustrated inFIG. 1. Alternatively, the molding process is performed after thetransfusion of two or more of the layers 22 to the current structure 16supported on the build platform 48.

In some embodiments, the build path 106 includes a bypass portion 106 athat bypasses the build path portion 106 b, along which the depositionunit 14 is positioned, as illustrated in FIGS. 1 and 4. In someembodiments, when multiple EP layers 22 are to be transfused to thestructure 16 before performing the molding process using the depositionunit 14, following the transfusion of an EP layer 22 to the structure16, the gantry 104 moves the build platform 48 and the supportedstructure 16 along the bypass portion 106 a (which may include thechiller 116) back to the transfusion assembly 40. After registering thebuild platform 48 or the structure 16 with the transfusion assembly 40,which may require lowering the build platform 48 using the gantry 104,another layer 22 is transfused to the structure 16 in accordance withembodiments described above. This process can be repeated as necessaryuntil the structure 16 is ready for the molding process. The gantry 104then moves the build platform 48 along the build path portion 106 b anda molding process is performed using the deposition unit 14 to form amultilayer molded part portion 22 mp within the one or more cavities 18of the structure 16, in accordance with one or more embodimentsdescribed herein.

In some embodiments, the system 10 allows at least the top portion ofthe structure 16 to be cooled before performing a molding process usingthe deposition unit 14. In some embodiments, following the transfusionprocess performed by the EP unit 12, the gantry 104 moves the buildplatform 48 with the supported structure 16 along the build path 106,such as along the build path portion 106 b, to the chiller 116, which isillustrated schematically in FIGS. 1 and 4. The chiller 116 operates tocool at least a top portion of the structure 16 supported on the buildplatform 48 before commencing the molding process using the depositionunit 14. The chiller 116 cools the structure 16 to sufficiently solidifyat least the portions of the structure 16 forming the cavity or partmold 18 that is to be used by the deposition unit 14 during the moldingprocess stage of the formation of the molded part. Exemplary embodimentsof the chiller 116 include a blower configured to produce air jets thatblow over the top surface of the structure 16, and/or other suitablecooling devices. After sufficiently cooling the structure 16, the gantry104 delivers the build platform 48 and the supported structure 16 alongthe build path 106 b and registers the build platform 48 and/orstructure 16 with the deposition unit 14 to allow for the commencementof a molding process using the deposition unit 14.

Exemplary embodiments of the deposition unit 14 are illustrated in thesimplified diagram of FIG. 5. FIG. 5 also illustrates the depositionunit 14 performing exemplary molding processes. While FIG. 5 illustratesa molding process being performed using a cavity or part mold 18 that isgenerally formed by a single EP layer 22 of the structure 16,alternative embodiments cover molding processes in which the cavity orpart mold 18 is defined by multiple layers 22 of the structure 16, asmentioned above.

The molding process performed using the deposition unit 14 allows thesystem 10 to produce a multi-material 3D part having one or more moldedpart portions 22 mp comprising molding materials 20 and one or moreprinted part portions 22 p comprising powder material, which may take onmany different forms. In some embodiments, the molding material 20comprises a material that is not conventionally used inelectrophotographic part producing processes, such as, for example,materials comprising electrically conductive particles such as metal,ceramic particles, large particles, or particles having a wide chargedistribution. This can allow for the use of materials that are notprintable by the EP engines 32 and/or without the additional cost todevelop and manufacture the materials into a toner or powder that may beused with the EP engines 12. In some embodiments, the molding material20 has a melt rheology that is similar to or substantially the same asthe melt rheology of the part material 86 p and/or the support material86 s of the electrophotographically formed layers 22 of the structure16.

Optionally, the combined electrophotographic and molding processesperformed by the system 10 allow for the formation of unique, composite3D parts. For example, when the illustrated portions 22 sp of thestructure 16 in FIG. 5 includes the part portions 22 p formed using theEP unit 12, the final 3D part produced by the system 10 includes boththe part portions 22 p and the molded part portions 22 mp. This allowsthe final produced 3D part to include part portions 22 p that protrudefrom the molded part, surround the molded part, and/or are enclosedwithin the molded part, for example. Typically, the part portions 22 pwould be formed from a different material type than is used to form partportions 22 mp, creating a two material part. Other configurations ofthe part portions 22 p and the molded part may also be achieved usingthe system 10. For example, more than two part materials may be used.When the structure 16 is only formed of the support structure portions22 s, the molded part forms the entire 3D part being produced.

In some embodiments, the deposition unit 14 includes a molding materialdispenser 120, which is configured to dispense the molding material 20over a top surface 121 of the structure 16 and into the one or morecavities 18 of the structure 16 using any suitable technique, asillustrated in FIG. 5. The dispenser 120 may comprise conventionalcomponents that are suitable for dispensing the molding material 20. Insome embodiments, the molding material 20 is in a powdered or granularform. In some embodiments, the molding material 20 is in a molten form.In accordance with this embodiment, the molding material dispenser 120may include one or more heaters to maintain the molding material 20 inthe molten form, or to transition the molding material 20, eitherpartially or completely, from a solid form (e.g., granular or powder) tothe molten form.

In some embodiments, the deposition unit 14 includes a spreading device122 that operates to spread the molding material 20 over the top surface121 of the structure 16 and into the one or more cavities 18, asillustrated in FIG. 5. Exemplary embodiments of the spreading device 122include a blade (shown) that extends across a width of the structure 16that is transverse to the direction 123 in which the gantry 104 feedsthe build platform 48 along the build path 106, or other suitablespreading device.

In some embodiments, the deposition unit 14 includes a heater 124 thatis configured to heat the molding material 20 within the one or morecavities 18 of the structure 16, as the build platform 48 and thesupported structure 16 are fed along the build path 106 by the gantry104. In some embodiments, the heater 124 includes a resistive heatingelement, a radiant heater, an infrared radiation heater, a hot airblower, and/or another suitable heating device.

In some embodiments, when the molding material 20 is in a powdered orgranular form, the heater 124 is configured to at least melt a portionof the molding material 20 within the one or more cavities 18. In someembodiments, the heater 124 is configured to fuse the powdered orgranular molding material 20 to itself. In some embodiments, the heater124 is configured to heat the molding material within the one or morecavities 18 such that it transfuses to the surfaces of the layer orlayers 22 that define the one or more cavities 18. In some embodiments,the heater 124 is configured to heat the powdered or granular moldingmaterial 20 to soften the powdered or granular molding material 20 andprepare the molding material 20 for a sintering process.

In some embodiments, the deposition unit 14 includes a pressing device126 that is configured to engage the top surface 128 of the moldingmaterial 20 within the one or more cavities 18, and press the moldingmaterial 20 into the one or more cavities 18, as illustrated in FIG. 5.In some embodiments, the pressing device 126 is configured to sinter themolding material, or a portion of the molding material, into the one ormore cavities 18 while the molding material 20 is in a softened orpartially melted state. In some embodiments, the pressing device 126includes a roller that is configured to roll over the top surface 128,as shown in FIG. 5. Other exemplary embodiments of the pressing device126 include a blade (not shown) that is configured to slide over the topsurface 128 of the molding material 20, or other suitable pressingdevice. In some embodiments, the functions of the spreader 122 and thepressing device 126 may be combined into a single roller, blade, orother suitable component, to both spread and press the molding material20 into the cavities 18. In some embodiments, the pressing device 126includes a heating element 127 that is configured to maintain thepressing device 126 at an elevated temperature that is greater than roomtemperature (25° C.), such as at a desired temperature for sintering themolding material 20.

In some embodiments, the pressing device 126 is located downstream ofthe heater 124 relative to the feed direction 123, as shown in FIG. 5.Alternatively, the pressing device 126 may be located upstream of theheater 124 (if present) relative to the feed direction 123.

In some embodiments, the nip roller 90 (FIG. 4) of the transfusionassembly 40, with or without the top-of-part heater 94, is used toperform the functions of heating the molding material 20, and pressingthe molding material 20 into the one or more cavities 18 of thestructure 16. Accordingly, the heater 124 and the pressing device 126 ofthe deposition unit may be eliminated. In some embodiments, followingthe deposition of the molding material 20 into the cavities 18 of thestructure 16, the build platform 48 is moved along the build path 106 tothe nip roller 90, and the nip roller 90 presses the molding material 20into the cavities 18. In some embodiments, the belt 44 at the nip roller90 is free from layers 20 during this pressing process. Additionally, insome embodiments, the nip roller 90 may apply heat to the moldingmaterial 20 as it presses the molding material 20 into the cavities. Insome embodiments, the top-of-part heater 94 is used to apply heat to themolding material 20 before it is pressed into the cavities 18 by the niproller 90.

In some embodiments, the system 10 includes a chiller 130 locateddownstream of the deposition unit 14 relative to the feed direction 123,as shown in FIG. 1. The chiller 130 operates to cool the moldingmaterial 20 within the cavities 18 and at least the top sections of thestructure 16. In some embodiments, the chiller 130 cools thesecomponents to the average temperature for the structure 16 that isdesired for performing the transfusion operation using the transfusionassembly 40. The chiller 130 may take on any suitable form, such as thatdescribed above with regard to chiller 116.

In some embodiments, the system 10 includes a planarization device 132that is located downstream of the deposition unit 14 relative to thefeed direction 123 (FIG. 1). In some embodiments, the planarizationdevice 132 is configured to planarize the top surface 128 of the moldingmaterial 20 within the cavities 18. In some embodiments, theplanarization device 132 is configured to planarize the top surface 121of the structure 16, which removes molding material 20 from the topsurface 121 of the structure 16, such as part portions 22 p and supportportions 22 s. Embodiments of the planarization device 132 include agrinder, a blade, or other conventional planarizing devices. In someembodiments, the planarization operation performed by the planarizationdevice 132 ensures that the top surfaces 121 and/or 128 of the structure16 and the molding material 20 are substantially flat and are preparedto receive additional EP layers 22 or molding material 20 in subsequenttransfusion and molding processes.

After the molding process is completed using the deposition unit 14, theone or more EP layers 22 of the structure 16 include only structureportions 22 s, or structure portions 22 s and one or more molded partportions 22 mp, as indicated by portions 22 sp in FIG. 5. The gantry 104moves the build platform 48 and the supported structure 16 with themolded part portions 22 mp along the build path 106 back to thetransfusion assembly 40 to begin another round of the transfusion andmolding processes as necessary to form a completed structure 16 thatincludes the molded part formed of the molded part portions 22 mp andthe structure portions 22 s, with the option of also including partportions 22 p. As discussed below, the structure portions 22 s may beremoved to reveal the final 3D part.

Exemplary embodiments of a method of producing a 3D part usingembodiments of the additive manufacturing system 10 will be describedwith reference to FIGS. 6-13. FIGS. 6-11 are simplified sidecross-sectional views of a structure 16 at various stages of the method.FIG. 12 is an exemplary completed structure 16 comprising a 3D part 140,and FIG. 13 is a side cross-sectional view of the structure 16 of FIG.12, taken generally along line 13-13. As discussed above, the portions22 sp are used to illustrate embodiments in which the structure 16includes only support portions 22 s, or both support portions 22 s andpart portions 22 p.

In some embodiments of the method, a structure 16 having at least onecavity 18, such as that illustrated in FIG. 6, is built on the buildplatform 48 in a layer-by-layer manner using the EP unit 12 inaccordance with one or more embodiments describe above. For example, atop layer 22 a of the exemplary structure 16 includes a structureportion 22 s, and at least one portion 22 sp that may be a structureportion 22 s or a part portion 22 p. In some embodiments, the portions22 s and 22 p are developed using the EP engines 32 s and 32 p, asdiscussed above with reference to FIGS. 1-3. The layer 22 a is thentransferred to the transfer medium 44, which feeds the transfer layer 22a to the transfusion assembly 40. The transfusion assembly transfusesthe layer 22 a to, for example, a bottom layer 22 of the structure 16,to form the structure 16 shown in FIG. 6.

In some embodiments of the method, the structure 16 is cooled on thebuild platform 48 using the chiller 116, exemplary embodiments of whichare shown in FIGS. 1 and 4. As mentioned above, this cools the structure16 in preparation for the molding process.

In some embodiments of the method, the molding process is performed onthe structure 16 using the deposition unit 14 in accordance with one ormore embodiments described above. For example, molding material 20 isdeposited into the one or more cavities 18 of the layer 22 a using thedispenser 120, as shown in FIG. 5, to form the molded part portion 22 mpof the structure 16, as shown in FIG. 7. In some embodiments, themolding material 20 is spread over a top surface 121 of the structure 16and into the one or more cavities 18 using the spreader 122 (FIG. 5).

In some embodiments, the molding material 20 is deposited into the oneor more cavities 18 when the molding material 20 is in a powdered orgranular state. In some embodiments, the step of forming the molded partportion 22 mp within the one or more cavities 18 involves heating themolding material 20 within the cavity, such as using the heater 124shown in FIG. 5. In some embodiments, this heating of the moldingmaterial 20 causes the molding material 20 to soften, melt, or fusetogether. In some embodiments, only a portion of the molding material 20in the cavities 18, such as a top surface or top portion, is softened,melted, or fused together, while the remaining portion remains in itsdeposited condition or different condition.

In some embodiments, the molding material 20 is deposited into the oneor more cavities 18 of the structure 16 when in a molten state. Inaccordance with this embodiment, it may not be necessary to further heatthe molten molding material 20, such as by using heater 124.

In some embodiments, the molding material 20 within the one or morecavities 18 is pressed into the one or more cavities 18 by a pressingdevice 126 (FIG. 5). In some embodiments, this operates to sinter themolding material 20 within the one or more cavities 18. In someembodiments, when only the top surface or top portion of the moldingmaterial 20 within the cavities 18 is softened, melted or fusedtogether, this pressing step causes the top portion of the moldingmaterial 20 to be sintered into the cavities 18. A post-productionprocess may later be formed on the molded part portions of the 3D part,such as the application of heat and pressure to finalize the 3D part.For example, a molded part portion 22 mp may be partially fused atmoderate temperatures and intermediate pressures as the 3D part isformed, then a final fuse may be performed when the part is fullyassembled at higher temperature and pressure.

In some embodiments, the molding material 20 within the one or morecavities 18 is cooled to solidify the molding material 20 and/or returnthe structure 16 to a desired temperature, such as a desired temperaturefor performing a transfusion process using the transfusion assembly 40,for example. In some embodiments, this cooling step may be performed bya chiller 130 shown in FIG. 1, for example.

In some embodiments, a top surface 128 of the molding material 20 in theone or more cavities 18 is planarized using the planarization device132. This ensures a uniform top surface 128 of the molding material 20,and can also remove molding material 20 from the top surfaces 121 of thelayer 22 a.

In some embodiments, the 3D part 140 is produced by adding one or moreEP layers 22 to the current structure 16 (FIG. 7) using the EP unit 12,and forming another molded part portion 22 mp within the one or morecavities 18 of each of the layers 22 using the deposition unit 14. Forexample, a layer 22 b may be transfused to the top surface of the layer22 a using the EP unit 12 to form the exemplary structure 16 shown inFIG. 8. Molded part portions 22 mp may then be formed within the one ormore cavities 18 of the layer 22 b using the deposition unit 14 to formthe structure 16 illustrated in FIG. 9. Subsequently, a layer 22 c maybe transfused to the top of the layer 22 b by the EP unit 12, and moldedportions 22 mp may be formed within the one or more cavities 18 of thelayer 22 c by performing embodiments of the molding process using thedeposition unit 14, resulting in a structure 16 shown in FIG. 10. Thecompleted structure 16 may then be formed by transfusing a layer 22 d onthe top surface of the layer 22 c using the EP unit 12, and moldedportions 22 mp may be formed within the one or more cavities 18 of thelayer 22 d by performing embodiments of the molding process using thedeposition unit 14, resulting in the structure 16 shown in FIGS. 12 and13.

One alternative to this process of transfusing the layers 22 and formingthe molded part portions 22 mp in a layer-by-layer manner, involvesbuilding a structure 16 having multiple layers 22 defining the one ormore cavities 18, and molding the part portions 22 mp within the one ormore cavities using the deposition unit 14. For example, the structure16 illustrated in FIG. 11 may first be formed using the EP unit 12 bydeveloping and transfusing the layers 22 a-22 d in a layer-by-layermanner. In some embodiments, this involves feeding the build structure48 along a bypass route 106 a (FIGS. 1 and 4), as discussed above. Afterthe multi-layered structure 16 is formed, molded portions 22 mp may beformed in the cavities 18 in accordance with embodiments of the moldingprocess described above. This generally involves moving the structure 16to the deposition unit 14 using the gantry 104, such as along the buildpath 106 b, depositing the molding material 20 into the one or morecavities 18, and possibly performing other method steps, such as, forexample, spreading the molding material 20 using the spreader 122,heating the molding material 20 using the heater 124, pressing themolding material 20 within the cavities 18 using the pressing device126, cooling the molding material 20 within the cavities 18 using thechiller 130, and/or planarizing the top surface 128 of the moldingmaterial 20 using the planarization device 132, to form the structureshown in FIGS. 12 and 13.

After the structure 16 with the molded part portions 22 mp is completed,such as illustrated by the exemplary structure 16 of FIGS. 12 and 13,the structure 16 may be removed from the system 10 and undergo one ormore operations to reveal the completed 3D part 140 formed by the moldedpart portions 22 mp and, optionally, the part portions 22 p. Forexample, the support portions 22 s may be sacrificially removed from the3D part 140 using an aqueous-based solution such as an aqueous alkalisolution. Under this technique, the support portions 22 s may at leastpartially dissolve in the solution separating the support portions 22 sfrom the 3D part in a hands-free manner.

In comparison, the molded part portions 22 mp and the part portions 22 pare chemically resistant to aqueous alkali solutions. This allows theuse of an aqueous alkali solution for removing the sacrificial supportportions 22 s without degrading the shape or quality of the 3D part 140.

Furthermore, after the support portions 22 p are removed, the 3D part140 may undergo one or more additional processes, such as surfacetreatment processes, a curing application such as one using ultravioletlight or heat, a sintering operation, or other process.

Although the present disclosure has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the disclosure.

What is claimed is:
 1. A method of producing a 3D part using an additivemanufacturing system comprising steps of: printing a layered structurehaving a cavity on a build platform from a powder material using atleast one electrophotographic (EP) engine and a transfusion assembly;molding a 3D part portion within the cavity including depositing moldingmaterial into the cavity using a deposition unit; and alternating theprinting and molding steps multiple times to form a 3D part.
 2. Themethod according to claim 1, wherein the layered structure comprises asacrificial support material
 3. The method according to claim 1, whereinthe layered structure comprises a sacrificial support material and apart material.
 4. The method according to claim 1, wherein: depositingthe molding material into the cavity comprises depositing the moldingmaterial into the cavity when the molding material is in a powderedstate; and molding a 3D part portion within the cavity comprises heatingthe molding material within the cavity to fuse together the moldingmaterial.
 5. The method according to claim 4, wherein molding the 3Dpart portion within the cavity further comprises pressing the moldingmaterial into the cavity.
 6. The method according to claim 1, andfurther comprising cooling the structure on the build platform beforeeach molding step.
 7. The method according to claim 1, whereindepositing the molding material into the cavity comprises depositing themolding material into the cavity when the molding material is in amolten state.
 8. The method according to claim 7, wherein forming a 3Dpart portion further comprises cooling the molding material within thecavity.
 9. The method according to claim 1, wherein forming the 3D partportion comprises planarizing a top surface of the molding materialwithin the cavity.
 10. The method according to claim 1, wherein printingthe layered structure comprises: forming at least one structure layerusing the at least one EP engine; transferring the at least onestructure layer to a transfer medium; and transfusing each structurelayer on the transfer medium to a top structure layer on the buildplatform.
 11. A method of producing a multi-material 3D part using anadditive manufacturing system comprising steps of: printing a structurehaving one or more layers on a build platform comprising: forming theone or more imaged layers of powder material using two or moreelectrophotographic (EP) engines; transferring the one or more layers toa transfer medium; and sequentially transfusing each of the one or morelayers on the transfer medium onto the build platform to form a layeredstructure having one or more cavities; wherein the layered structureincludes a sacrificial material portion and a part portion; and forminga molded part portion within the cavity including depositing moldingmaterial into a cavity of the structure using a deposition unit; andrepeating the printing and forming steps multiple times to form acombined structure comprising a 3D part and a sacrificial supportstructure, wherein the 3D part includes the part portion of the layeredstructure and the molded part portion.
 12. The method according to claim11, wherein: depositing the molding material into the cavity comprisesdepositing the molding material into the cavity when the moldingmaterial is in a powdered state; and forming a molded part portionwithin the cavity comprises heating the molding material within thecavity to fuse together the molding material.
 13. The method accordingto claim 11, and further comprising cooling the layered structure on thebuild platform before each forming step.
 14. The method according toclaim 13, wherein forming a molded part portion comprises at least oneof heating the molding material and pressing the molding material intothe cavity.
 15. An additive manufacturing system for producing 3D partscomprising: a build platform; an electrophotographic additivemanufacturing unit comprising: a transfer medium; at least one EP engineconfigured to develop layers of a powder material and transfer thelayers to the transfer medium; and a transfusion assembly configured tobuild a structure having a cavity on the build platform in alayer-by-layer manner by transferring the developed layers from thetransfer medium and fusing them together using heat and pressure; and adeposition unit configured to deposit molding material into the cavityand form a molded part portion of a 3D part within the cavity.
 16. Thesystem according to claim 15, wherein the deposition unit includes aheater configured to heat the molding material within the cavity. 17.The system according to claim 16, wherein the deposition unit includes apressing device configured to engage a top surface of the moldingmaterial within the cavity and press the molding material into thecavity.
 18. The system according to claim 17, wherein the depositionunit comprises a spreading device configured to spread the moldingmaterial into the cavity of the structure on the build platform.
 19. Thesystem according to claim 15, further comprising a gantry configured tofeed the build platform and the structure between theelectrophotographic additive manufacturing unit and the deposition unitalong a build path.
 20. The system according to claim 19, wherein thebuild path includes a by-pass route that avoids the deposition unit.